Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management

Abstract

Small intestinal bacterial overgrowth (SIBO) is a common, yet underrecognized, problem. Its prevalence is unknown because SIBO requires diagnostic testing. Although abdominal bloating, gas, distension, and diarrhea are common symptoms, they do not predict positive diagnosis. Predisposing factors include proton-pump inhibitors, opioids, gastric bypass, colectomy, and dysmotility. Small bowel aspirate/culture with growth of 10-10 cfu/mL is generally accepted as the "best diagnostic method," but it is invasive. Glucose or lactulose breath testing is noninvasive but an indirect method that requires further standardization and validation for SIBO. Treatment, usually with antibiotics, aims to provide symptom relief through eradication of bacteria in the small intestine. Limited numbers of controlled studies have shown systemic antibiotics (norfloxacin and metronidazole) to be efficacious. However, 15 studies have shown rifaximin, a nonsystemic antibiotic, to be effective against SIBO and well tolerated. Through improved awareness and scientific rigor, the SIBO landscape is poised for transformation.

Figure 1.

Description of the procedure for duodenal aspiration, specimen collection, and handling: The technician flushes the scope with sterile water and prepares a sterile field. A Liguory catheter with a stopcock is assembled (a). The scope is passed into the second/third portion of the duodenum with minimal air insufflation and suctioning. The endoscopist and the technician wear sterile gloves and advance the Liguory catheter through the biopsy channel. The technician performs gravity-assisted aspiration by holding the syringe at a height lower than the patient to aid fluid flow. Using gentle suction, ∼3 mL of duodenal fluid is collected and immediately transferred to the microbiology laboratory (b).

Figure 2.

Typical example of breath test results: Shown are a negative breath test result (a), a positive hydrogen breath test showing hydrogen concentration rising >20 ppm from baseline (b), and a positive breath test showing methane concentration rising >10 ppm from baseline (c). Red lines show hydrogen concentrations, and black lines show methane concentrations. Duodenal aspirates and culture results are shown in the text inset of (b).